we have always used our boats throughout the year, and they used to have more use in winter than summer when we had big cod to go and fish for..we haven't any longer but thats another story
As said ensure the water can drain out after flushing by trimming the engine all the way down, and back up and down again to ensure there are no trapped bits of potential ice! We never winterise the motors but I do ensure that they come out of the garage and are run for a time on flush muffs at least once a month, the steering is turned and the trim used - lack of use being an outboards main threat. And then be sure to drain down as above.
A four stroke motor is not a sealed coolant thing, there is no water jacket to add antifreeze to, its all raw water.
In all the years at the boat club I have only seen one outboard go bang in the winter due to freezing up-poor Harry lives up in the hills and its cold up there! Launched the boat after towing it 60 miles or so to the club, started it up and it ran just long enough for him to be far enough out to sea to need a tow home when it blew the core plugs out!
Winter boating is the best thing in the world....when you think about it in summer!! When it gets to february its not always as appealing so it may be an idea just to winterise if you are not so sure as to if you will use it.